The present application relates to electronic lighting. It finds particular application in connection with providing electrical decoupling in lighting ballasts and will be discussed with particular reference thereto. It is to be appreciated, however, that the present application can also be used in other lighting applications, and is not necessarily limited to the aforementioned application.
There is an ever increasing demand in the lighting industry for smaller lighting packages. More particularly, there is a demand for increasingly higher power ballasts in smaller, more compact housings. Accordingly ballast designers, faced with this industry demand, must design ballasts to be smaller and have a greater power capacity.
Typically, electronic ballast designs use more than one magnetic component. The magnetic components can be for an electromagnetic interference (EMI) filter, for power factor correction, or for a ballast design that uses inductors and transformers. One magnetic component could also be used, but this approach is typically disfavored because the component would be relatively large. Thus, in order to reduce the overall size of the ballast, multiple magnetic components are used either in series, in parallel, or a combination of the two in both primary and secondary windings.
In the case where two transformers are situated in parallel in both the primary and secondary windings, circulating current will occur between the transformers if the electrical parameters of the windings are not matched exactly. That is, there is electrical interference with both the primary and secondary windings of the two transformers that are connected in parallel. As a result, the transformers will produce added heat, increase the possibility of overheating, and generally degrade the performance of the circuit.
Thus, a need exists for an improved electronic ballast design that includes at least two transformers that can be smaller, low profile components that effectively handle higher power and high current, and which allow the two transformers that are connected in parallel to be effectively decoupled so that the primary and secondary windings do not cause circulating current between the two transformers.